1. Field of the Invention
The technical field of this invention is in the area of electronic data processing. More particularly, the invention relates to data structures, methods, computer program products and systems for accessing data objects, particularly in the context of data moving.
2. Description of the Related Art
Moving of data objects is well known to every user of a computer and is a standard procedure, which is routinely applied. A special application of moving data objects is the archiving process, by which data objects are moved from a first to a second storage location for safety and/or performance reasons. In enterprises, enterprise resource planning software (ERP) applications are used to control or support business processes and the management of the enterprise. ERP software is further used to manage company information of enterprises of various kinds in any field of technology by means of automatic data processing systems such as computers or computer systems. During the use of such software a huge amount of data is usually created, which contains important business information and which has to be archived from time to time.
According to the state of the art (see Helmut Stefani, Datenarchivierung mit SAP, Galileo Press GmbH, Bonn 2002, ISBN 3-89842-212-7), archiving can be performed automatically by archiving software tools, which can be part of the ERP software. Such tools can consist of a writing module, which stores (writes) the data objects to be archived sequentially in archive files, and a deleting module, which deletes the successfully archived data from the original data object base. The writing module can select the data objects to be archived from the data base according to specific criteria, e.g. the creation time of the data. It usually does not modify the original data objects or data base. The deleting module staggeredly reads the archive file sequentially and deletes the data objects found in the archive file from the original data base. This ensures that only such data objects are deleted from the original data base, which are readably stored in the archive file. The time for the archiving procedure as a whole depends on the amount of data and varies from a few milliseconds to several hours or days. Consequently, there is in many cases a considerable time gap between writing the data into the archive file and deleting the data from the original data base. This time gap can be a reason for the following problems:
As long as the data objects are still available in the original database, they can still be modified by any software application during the time gap. Because the deleting program does not compare the archived data object and the data object to be deleted, such modifications can be lost. This has not only the consequence of the loss of the amended data, it can additionally have the consequence that certain business processes can not be completed.
Another problem arises if several archiving processes run in parallel. In this scenario, that one data object can be archived several times, and no longer unambiguously identifiable. This can have the consequence that evaluations or statistical analysis, which use the archive files, produce wrong results.
It is also possible that data objects in the original database are read by the writing module and are simultaneously modified by an other software application. In such a case, the data can be transferred from an archiveable status to a non-archiveable status. As a result, data objects which are not archiveable are written into the archive file and are deleted from the original database. In effect, this can result in a loss of data.
Thus, there is a need for a data structure, method, software application and/or data processing system providing a more efficient solution of the problems described above, particularly it is desirable to provide a data structure for enabling an effective prevention of the modification of a data object during a moving or archiving process.